A pet hate of mine is complex diagrams that I cannot read on my laptop without zooming in and out and scrolling around. They may be fine for posters that are put on a wall but they are not generally useful architectural artifacts.
I am going to state the obvious – most people look at documents and diagrams on screens or on printouts that they carry around. The size of these is pretty consistent at around A4 size. If you cannot read and understand a diagram that is that size then the diagram is a waste of effort. So, please have some consideration for your audience when creating diagrams – it is a simple and common courtesy.
But I said it is “bad architecture”, surely this is bad presentation. First, since communication is critical for architects, then poor communication is bad architecture. However, the point is deeper than this…
Good architecture is well modularised. It is separable logically. A large complex domain can be decomposed into multiple simpler domains with clean simple interfaces between them. This implies that a set of hierarchical diagrams can be created to represent the architecture each of which can be understood on their own and with sufficient contextual information. So, going back to the communication point. If the architecture is good then it can be presented simply. Is there any benefit in making simplicity appear complex?
What about the as-is? If the current architecture is a mess of spaghetti then how can this be represented simply. Well, this is a core part of the architecture skillset! Logical partitioning is a critical step towards resolving the mess. In short, you must partition it logically as you would a good to-be architecture and what you will be showing is that interfaces are not clean and the components are not well formed. This gives you a start point for refactoring. Showing a mess by producing complex diagrams highlights the problem but does not help solve it.
Please don’t produce complex diagrams, there is no need, ever! I do not want to waste my time trying to understand another diagram with 200 blobs and 500 lines on my laptop again. The person who produced this diagram had the knowledge and has singularly failed to transfer it effectively. That is bad architecture and failure for an architect!